158 



HELMINTHOZOA. 



Fig. 78. 



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t 



(422.) Around the mouth or anterior part 

 of the oesophagus there appears to be a 

 delicate nervous ring, probably specially con- 

 nected with the association of such move- 

 ments of the oral extremity as are essential 

 to the imbibition of nourishment. Prom 

 this oral ring proceed two long nervous 

 filaments (fig. 78, e e}, one of which runs 

 backwards along the dorsal aspect of the 

 body, while the other occupies a similar 

 position upon the ventral surface. The last- 

 named filament is described by Cloquet as 

 dividing, in the female Ascaris, at the 

 point where the termination of the organs 

 of generation issues from the body (fig. 78, 

 1, m), so as to enclose the termination of 

 the vagina in a nervous circle. 



(423.) The digestive apparatus in this 

 order of intestinal worms is very simple. 

 In Ascaris lumbricoides the aperture of the 

 mouth (fig. 78, a) is surrounded by three 

 minute rounded tubercles; into each of 

 these, fasciculi, derived from the longitu- 

 dinal muscles of the body, are inserted in 

 such a manner as to cause the separation of 

 the tubercles and consequent opening of 

 the mouth, which is again closed by a 

 sphincter muscle provided for the purpose. 

 To the mouth succeeds a short oesophagus 

 (fig. 78, 1 & 2, 5), which is separated by a 

 constriction from the rest of the alimentary 

 canal, and would seem, from the muscularity 

 of its walls, to be an agent employed in 

 sucking-in the liquid food upon which the 

 creature lives. The true digestive cavity 

 (fig. 78, 1 & 2, c c) is a simple and extremely 

 delicate tube, which arises from the oeso- 

 phagus, and, without presenting any appear- 

 ance indicative of separation into stomach 

 and intestine, gradually enlarges as it pro- 

 ceeds backwards, until it terminates at the 

 hinder extremity of the body by a narrow 

 aperture (fig. 78, 1 & 2, d). 



Anatomy of Ascaris lumbricoides. 1. Female Ascaris : a, oral orifice; b, muscular oesophagus 

 c, alimentary canal ; d, termination of ditto at the posterior extremity of the body; e, nervous flla 

 incuts; k, convolutions of the two ovigerous canals; I, uterine receptacle. 2. Male Ascaris 

 o, 6, c, d, e, as above ; /, convolutions of the testes ; g, its terminal dilatation, ending in i, the penis 



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